In contemporary filmmaking and in other applications such as newscasts, chroma keying is commonly used to change a background or remove an object (or part of an object) from an image. To change the background, for example, a scene is “filmed” (recorded) in front of a green screen or blue screen. The portions of the recorded image that match the color of the screen are then removed digitally. The removed portions can then be replaced with a different background to form an image that is a composite of the recorded image and the new background.
Conventional chroma keying can be challenging. For one thing, the color of the key (e.g., green) cannot appear in the scene outside the portion that is to be removed and replaced, because all parts of the recorded scene that include the color of the key will be replaced in the composited image. If, for example, a character wears green in front of a green screen, the green part of the character's clothes will be replaced as well as the green background. Conventional chroma keying can also make recording a scene more complex when, for example, one character is wearing green and the other character is wearing blue. The green-clothed character would need to be filmed in front of a blue screen, and the blue-clothed character in front of a green screen.